The present invention relates to a device for the stimulation of a body part and to a method for the stimulation of a body part with the aid of an external stimulation device.
The treatment of centrally induced paralyses is one of the central problem areas in medical research. Central paralyses may occur on account of brain damage or spinal cord injuries. They are frequently caused by stroke syndromes, congenital brain damage, brain tumours or external injuries. Central paralyses are often accompanied by painful spastic muscle cramps. At present, they cannot be adequately cured by either surgery or medication.
Central paralyses can currently only be treated by conventional physiotherapy or by activating nerves or muscles of the paralysed body part by electric stimuli. For this purpose, electrodes are attached on or under the skin of the paralysed body part, so that an electric field is generated in the region of the nerves or muscles to be activated of the paralysed body part. This can only lead to a restricted reactivation of the muscles. Permanent rehabilitation, and consequently curing of the paralysis, cannot be achieved in this way however. What is more, considerable pain often occurs in this treatment.
U.S. Pat. No. 5,620,463 discloses an electrophysiological conditioning system which has conditioning applicators which transmit electromagnetic conditioning signals suitable for bringing about basic physiological effects, such as relaxation of the nervous system, stimulation of the blood circulation and stimulation of normal cell repair and regeneration, and are suitable for enhancing the natural self-defence and healing mechanisms of man and animals. For this purpose, magnetizing coils, which generate a magnetic field when a current pulse is discharged through the coil, are used. Such a conditioning system is not suitable, however, for the treatment of central paralyses.
The object of the present invention is to provide a method and a device for the treatment of central paralyses in such a way that a permanent rehabilitation effect is brought about.
The invention provides a device and a method for the stimulation of a paralysed body part, with the aid of which a smooth and pain-free composite and coordinated movement of the body part concerned can be induced. The failure of the proprioceptive afferences (biosensors, for example neuromuscular spindles) caused by the paralysis is to be replaced as far as possible to stimulate the plastic capabilities of the central nervous system as early as possible by a neuromodulation.
The device according to the invention for the stimulation of a body part has at least the following elements: at least two coils Si with at least one power supply for the generation of magnetic fields at innervation zones of the body part, particularly preferably at end branches of motor nerve fibres and peripheral nerves, and a device for the open-loop or closed-loop control of the power supply (supplies) for the coils. In this case, the device for the open-loop or closed-loop control of the power supply (supplies) for the coils has at least a current pulse generator for the emission of current pulses I (Si) at pulse frequencies f (I(Si)) and pulse durations d (I(Si)) through the power supply (supplies) to the coils Si, the emission of the current pulses taking place in such a way that the respective magnetic field pulses generate an electric field in the nerve paths, so that muscles of the body part are contracted or decontracted in a coordinated manner, so that a coordinated composite movement of the body part is obtained. This [lacuna] takes dependent factors into account, and an adaptation to neuronal erethisms takes place.
The device according to the invention consequently allows the generation of precisely defined movements of the centrally paralysed body part. These movements are often composed of a number of partial movements and simulate natural movements of the patient as faithfully as possible, for example grasping movements or walking movements. By a repetitive magnetic stimulation, primarily proprioceptive afferences are initiated both adequately by the induced movements and by direct activation of afferent nerve fibres. A regular repetition of induced movements can bring about a learning effect in the central nervous system, finally leading to the patient being able to perform the induced movements again independently (actively) with the paralysed body part. Starting from this partly rehabilitated state, the patient can then also re-learn other movements.
This method can basically be used for the treatment of any centrally paralysed body parts. It is not technically restricted to humans, but can also be used in the case of animals, for example racehorses, with local symptoms of paralysis.
The device according to the invention may have two or more coils Si. Preferably three, four or five coils are used for the stimulation of the paralysed body part. For simple movements, a single coil may also be used. These coils must be of such a type that they can be positioned over innervation zones of the paralysed body part in such a way that an electric field is produced there by induction when a current pulse I (Si) passes through the coil Si.
Each coil Si preferably has a power supply, which generates the current pulses I (Si) necessary for generating magnetic fields. However, a common power supply may also be used. These power supplies are controlled by a current pulse generator, which prescribes the point in time, frequency, duration and intensity of the current pulses I (Si).
The current pulse generator generates the current pulses on the basis of prescribed patterns, which respectively correspond to certain composite sequences of movements, to be specific the physiological sequences of movements of the body part concerned. For this purpose, a multiplicity of patterns can be kept in a storage medium, which the current pulse generator can access at any time and which it can modify.
The intensity of the current pulses I (Si) determines the field strength of the magnetic field respectively generated. The field strength of the magnetic field applied must exceed a certain threshold in order for a movement to be initiated. This threshold may vary with the body part concerned and with the patient.
The duration and frequency of the current pulses influence the performance of the induced movements, that is to say their roundness or angularity, to a considerable extent. However, the duration and frequency of the current pulses also have a great influence in the area of therapy. The pulse frequency f (I(Si)) preferably lies in a range from 10 Hz to 30 Hz, particularly preferably in a range from 15 Hz to 25 Hz. These frequencies lie in the physiological range for activating the muscles. A current pulse preferably corresponds here to a sinusoidal oscillation, on account of the optimization in terms of energy. The sinusoidal oscillation preferably has here, again with regard to its optimization in terms of energy, a period duration in a range from 1.9*10xe2x88x924 s to 3.77*10xe2x88x924 s, particularly preferably in a range from 1.19*10xe2x88x924 s to 2.15*10xe2x88x924 s. The segment extends preferably from 0 to a value in a range from 0 to 2xcfx80, particularly preferably to a value of k*xcfx80/4, where k is 1, 2, 3 or 4. In a further preferred embodiment, the sinusoidal oscillation is broken off at a value in the range from 0 to xcfx80/4, so that a high value for dI (Si)/dt is obtained, which brings with it an improved stimulation effect.
In a preferred embodiment, the device for the open-loop or closed-loop control of the power supply (supplies) for the coils Si has at least one sensor for sensing the momentary position of the body part, in order in this way to be able to control or regulate the power supply (supplies) for the coils correspondingly. Preferably, one or more, possibly also a combination, of the following sensors is used here: a position switch, preferably a 3-point switch, an angle potentiometer, an ultrasonic measuring system or an infrared camera. If angle-measuring potentiometers are used, an arrangement of three potentiometers, the angle signals of which are summated, is preferably chosen. As a result, the individual potentiometers do not have to be adapted exactly to the axis of the joint. In the case of an ultrasonic measuring system, ultrasonic transmitters are fastened at suitable points of the body part concerned. The signals of these transmitters are sensed by a fixed receiver with regard to their position. If infrared cameras are used, the position is calculated back from the image of two cameras by means of infrared LEDs fastened at suitable points of the corresponding body part.
In another preferred embodiment of the device, the device is specifically adapted to a particular patient, so that the device can also be used in a xe2x80x9cfeed-forwardxe2x80x9d mode without any sensors.
The device for the open-loop and closed-loop control of he power supply (supplies) for the coils preferably includes a closed-loop control unit which responds to a signal which represents at least one state parameter for at least one muscle of the body part. The state of a muscle comprises the mechanical expansion (elastic and damping factors) and the innervational, contractile muscle activation. This signal is preferably obtained from an electromyogram, which is measured at least one muscle of the body part. Electromyography represents a method of registering muscle action potentials. An electromyogram can consequently provide information on induced or voluntary, intended action potentials, by which the stimulated movement of the muscle concerned is supported. Consequently, not only the degree of paralysis and the rehabilitation already achieved but also the fatigue of the muscle can be determined. The influence of the support of the induced movements by the patient as a result of the patient""s own willpower can also be quantitatively or qualitatively assessed with the aid of this method. This information makes it possible to adapt the current pulses I (Si), that is to say their intensity, frequency and duration, to the specific treatment situation of the patient. In this way, the rehabilitation can be individualized and intensified.
The closed-loop control of the treatment can in principle take place at any time intervals, for example after every few seconds, which would mean constant monitoring of the situation, or else after every few days or weeks, which would be equivalent to keeping a general watchful eye on the rehabilitation steps.
In a further preferred embodiment of the invention, the device for the open-loop or closed-loop control of the power supply (supplies) for the coils Si has at least one sensor for sensing forces acting on the corresponding body part, to make it possible in this way for the power supply (supplies) for the coils to be controlled or regulated in an adapted manner. This sensor is preferably a pressure-dependent resistor. For this purpose, a piezoelectric capacitance measurement is carried out, for example, or strain gauges are used.
Preferably, a learning ;algorithm is integrated in the device for the open-loop or closed-loop control of the power supply (supplies) for the coils. During a stimulation, the stimulation result and effect are observed, analysed and recorded in a memory unit. This allows the stimulation effect to be optimized patient-specifically in successive cycles. As an alternative to this, the procedure may also be such that the movement is initially performed under open-loop control, after completion of the movement the actual position of the body part is compared with its desired position and then the control parameters are changed in such a way that the aim is achieved even better when the next stimulation is carried out. This type of xe2x80x9cfeed-forwardxe2x80x9d control corresponds more closely to the physiological situation. This control can be realized for example by several neuro-controllers (neuronal networks) or by an adaptive control device. In a further possible way of using the learning algorithm, the stimulation pattern is adapted to the physiological generation of signals.